Time capsule backup speed when its not the router

I have a new Time Capsule which I have connected to my existing Modem/Router as an ethernet device, so it is not running as the router itself. However I have set it up to run its own wireless network.

I am trying to do the first backup of my mac mini, with attached external hard drive which has my iTunes library. The size of the backup is about 380gb. I connected the mac mini to the Time Capsule wireless network, and started the backup, but is running quite slowly, at about 5gb per hour. So the full backup will take about 3 or 4 days at this rate. The initial backup of my MacBook Pro (about 18gb) took 2 or 3 hours, so a similar sort of speed. I've disabled Time Machine on the Macbook pro for the time being, until I get the mac mini sorted out.

I understand a backup over ethernet would be quicker, but the time capsule is not the network router, so if I just connect an ethernet cable from the mac mini to the time capsule, is that going to work?

Is my only option to use the Time Capsule as router? Or is there anything else I can try?

 

Thanks skorpien, that makes sense and it works just as you say. I should have just tried it I guess, but I didn't want to risk messing up the backup in progress. It's still going to take a while, but compared to the wireless option, it is flying along.